Re: Coolant temperature sending unit readings

Posted by HH56 On 2024/4/27 18:53:50

48-50 models use a different gauge system than other years so fuel, oil, and temp senders do not have a specific resistance value. While other years use a changing resistance, the 48-50 models use a pulsing contact which is either on or off and connects straight to ground. The frequency and duration of the pulse depends on how the temp, pressure, or fuel level biases the bimetal strip in the sender to change the length of time the heater needs to change the temperature of the bimetal and make it work the contact. Some Ford products also used this same gauge system.

Here is a bit from an old Motor's Manual explaining the 48-50 system operation and also an oscilloscope photo of a gauge with fuel sender showing the pulsing action. Ford products mostly used two senders but Packard used a single temp sender so needs the single terminal sender. If you need a new sender, BDeB has said 40-55 Ford senders will work electrically and Dennis Carpenter Ford Parts has made repros. I don't know if anyone has tried the Ford sender in their Packard so do not know if the size thread Ford used for their head port is the same. If you do need a new sender and decide to try the Ford version please let us know if it fits.

Attach file:

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  48-50 K-S temp ga.jpg (570.16 KB)


  22-23 bimetal sender action.jpg (167.91 KB)